1. Field of the Invention
Apparatuses consistent with the present invention relate to an intenna-type dipole antenna for receiving broadcast signals in a very high frequency (VHF) band, and more particularly, to an intenna-type dipole antenna which is mounted as the intenna to receive broadcast signals in a VHF band.
2. Description of the Related Art
With advances in mobile communication technologies, wireless terminals are providing various services that have been available only in limited places such as home or offices.
Among those services, recently, much attention is paid to digital multimedia broadcasting (DMB) or digital video broadcasting-handheld (DVB-H) which receives and services broadcast signals in a very high frequency (VHF) band.
The DMB service or the DVB-H service, which is a mobile multimedia broadcast service of new idea with convergence of communicating and broadcasting, enables the viewing of broadcast programs in the VHF band through wireless terminals.
The DMB service is provided through wireless mobile terminals such as a dedicated DMB terminal, a notebook computer, a mobile phone terminal, a vehicle mounted terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), and the like. The DMB service is classified into a satellite DMB service and a terrestrial DMB service. The terrestrial DMB service uses a frequency band of 176-212 MHz, and the satellite DMB service uses a S-band of 2.630-2.655 GHz which is higher than the terrestrial DMB band.
Typically, a length of a dipole antenna is λ/2 and that of a monopole antenna is λ/4. Accordingly, the higher a frequency band is, the shorter an antenna is, and the lower a frequency band is, the longer an antenna is. Since the terrestrial DMB service uses the VHF band commonly used for broadcasting, it needs a longer antenna than the satellite DMB service and the same antenna size as the TV antenna in theory. Hence, the terrestrial DMB service requires the antenna length above about 30 cm. When the antenna output is high, the length of the antenna may be shorter.
The terrestrial DMB has very small output of about 1-2 KW because it uses taboo channels 8, 10 and 12. Since the channel 8, which is between the channel 7 and the channel 9, causes radio interference to the neighboring channels when its output is increased, it is hard to raise the output of the channel 8. However, when such an antenna is mounted in a wireless terminal which features portability and mobility, it is inconvenient to use a longer antenna.
Thus, the most urgent task to antenna developers is to shorten the length of the terrestrial DMB antenna while the reception sensitivity is maintained. It is known that it is almost impossible to implement the terrestrial DMB antenna below 15 cm in length up to now.
In the mean time, the DVB-H, based on digital video broadcasting-terrestrial (DVB-T) developed and adapted for digital TV broadcast standard primarily in Europe, is one of the DVBs taking account of low power, mobility, and portability of mobile phones or portable video devices. As the DVB-H utilizes a relatively low frequency band, it may face the same problems as the terrestrial DMB antenna.
Therefore, it is demanded to develop an antenna that can be embedded in a device as an intenna to receive signals in the VHF band used mostly for the terrestrial DMB service or the DVB-H service.